Quantitative Analysis of Retinal Vascular Parameters in Patients with Normal Tension Glaucoma

Abstract

Purpose : To investigate macular and optic disc area vascular parameters in patients with normal tension glaucoma (NTG) using optical coherence tomography angiography (OCTA).

Methods : In this IRB-approved cross-sectional study, images were prospectively acquired from both eyes of 26 patients with clinically-diagnosed NTG and 22 age-matched volunteers with normal healthy eyes using the Zeiss swept-source (SS) OCTA (Plex Elite 9000, Carl Zeiss Meditec). Vascular parameters within a 5 mm diameter disc area centered over the macula and optic nerve head were analyzed. Following projection artifact removal, OCTA images were binarized and skeletonized for quantitative analysis and calculation of perfusion density (PD = binarized vessel area/ analyzed area) and vessel length density (VLD = total length of skeletonized vessels/ analyzed area) (Figure 1). PD of the choriocapillaris (CC), and PD and VLD of superficial vascular plexus (SVP), deep capillary plexus (DCP), and superficial optic nerve head + peripapillary area (ONH + PP) were computed and compared between groups.

Results : The final analysis cohort included 50 eyes with NTG and 40 healthy control eyes. Mean age was 60±10 years in the NTG group and 60±17 years in the control group.
NTG group had a statistically significant reduction in PD of CC compared to normal controls (71.75±8.28 % vs. 80.48±3.84 %, p<0.001). There was not a statistically significant difference in PD between NTG and control group for SVP (51.33±3.44 % vs. 50.45±3.45 %, p=0.26), DCP (47.89±3.76 % vs. 47.52±3.59 %, p=0.54) and ONH + PP (54.45±5.73 % vs. 55.23±3.58 %, p=0.78).
NTG group also presented statistically significant reductions in VLD compared to normal controls: SVP (2084.59±152.33 mm/mm² vs. 2154.63±144.18 mm/mm², p=0.02) and ONH + PP (1818.44±270.94 mm/mm² vs. 1950.23±169.33 mm/mm², p=0.03), while the DCP VLD was similar between the two groups (2292.01±149.15 mm/mm² vs. 2256.49±133.73 mm/mm², p=0.22).

Conclusions : Eyes with normal tension glaucoma appear to show a lower CC perfusion density, as well as a lower SVP and ONH + PP vessel length density compared to normal eyes. OCTA-based vascular alterations may warrant further study.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Figure 1. Projection-resolved OCTA images of the retinal vascular layers: superficial vascular plexus (SVP) (1A); deep capillary plexus (DCP) (1B); choriocapillaris (CC) (1C); and superficial optic nerve head + peripapillary area (ONH + PP) (1D).